1. Field of the Invention
This invention relates generally to adhesives and, more particularly, to quick-setting adhesive compositions based on .alpha.-cyanoacrylates which contain .alpha.-, .beta.- and/or .gamma.-cyclodextrin derivatives at least partly soluble in the cyanoacrylates.
Adhesive compositions based on .alpha.-cyanoacrylates are capable of curing in a very short time and are eminently suitable for bonding a number of materials. Cyanoacrylate adhesives are generally cured by anionic polymerization initiated by only small traces of even weak bases, such as water or methanol. Problems arise in the use of these adhesives for bonding porous materials and for bonding substrates having surfaces showing an acidic reaction which inhibit the anionic polymerization of the .alpha.-cyanoacrylate. For example, setting times of up to 20 minutes are required in the bonding of cellulose-containing materials, quite apart from the fact that the bond strength of the joined materials is often unsatisfactory.
Now, various attempts have been made to shorten the setting times, even in the case of problematical materials.
2. Discussion of Related Art
DE-OS 28 16 836 describes .alpha.-cyanoacrylate adhesives with shortened setting times which contain at least one macrocyclic polyether compound (crown ether) selected from the group of macrocyclic polyethers and their analogs as setting accelerator. According to European patent application 142 347, crown compounds containing silicon atoms are added to the cyanoacrylates as accelerators in quantities of 0.1 to 5%. However, these adhesive compositions have certain negative properties. For example, their stability in storage is in need of improvement.
Accordingly, the problem addressed by the present invention was to find other additives which would significantly shorten the setting times of cyanoacrylates without adversely affecting their stability in storage